MELBOURNE, Florida (Reuters) – President Barack Obama defended his policy on outer space and warned seniors that Republicans would raise their healthcare costs during a campaign stop on Sunday in Florida, where he is seeking to sway undecided voters to help him win the state.

The Democratic incumbent is wrapping up a two-day bus tour of this political battleground state after making targeted appeals to specific voting blocs he needs: independents, Latinos and senior citizens.

On Saturday he bought lunch at a Cuban restaurant to woo Hispanics and campaigned with former Republican Governor Charlie Crist to entice independents.

On Sunday he slammed his opponent, Republican Mitt Romney, over his plans for Medicare, the popular healthcare program for the elderly. Romney’s running mate, congressman Paul Ryan, proposed a plan two years ago that would transform Medicare into a program in which recipients would use vouchers to buy private insurance.

“Here’s the bottom line: Their voucher plan for Medicare would bankrupt Medicare. Our plan strengthens Medicare,” Obama told an enthusiastic crowd of some 3,000 at an indoor rally.

He cited a report that showed costs for the program would rise dramatically as a result of the Republicans’ proposals.

Romney’s campaign said the report was not neutral and called Obama’s attacks untrue.

“(Obama) has done nothing to reform Medicare for the long haul and prevent it from going bankrupt, and on his watch family health care premiums have increased by nearly $2,500,” Romney spokesman Ryan Williams said in a statement.

“The president’s decision to use discredited studies and outright falsehoods to attack Mitt Romney is an admission that he can’t talk about his record of crushing the middle class and failing to turn the economy around.”

Obama’s campaign sees the Medicare issue as a winner, even as it recognizes the economy – the main issue of the November 6 election – as the president’s greatest weakness.

“If they want to have a discussion about who do you trust on Medicare for the next 60 days as their central argument, you know we ought to send them an in-kind contribution,” Obama adviser David Plouffe told reporters on Air Force One last week.

But a disappointing jobs report on Friday gave fodder to Romney, whose central argument has been that Obama’s stewardship of the economy is Exhibit A for why he should be replaced.

SPACE, ISRAEL

The president picked a tricky spot in Florida to make his case. The Melbourne area supported Republican nominee John McCain in 2008 by a wide margin, but demographic changes have made the area more friendly to Democrats, an Obama campaign official said.

Mindful of the importance of the space industry to voters in a part of the state that includes the Kennedy Space Center, Obama defended his administration’s handling of the space program during the rally.

“Here on the space coast we’ve started a new era of American exploration that is creating good jobs right here in this county. We’ve begun an ambitious new direction for NASA by laying the groundwork for 21st century space flight and innovation,” he said.

One woman in the crowd repeatedly yelled “What about Israel?” during the rally.

In an embarrassing turnaround at the Democratic convention on Wednesday, delegates reinstated language in their party platform declaring Jerusalem to be the capital of Israel after Obama objected to it being dropped and Republicans accused them of showing weak support for the longtime U.S. ally.

Romney’s campaign has continued to press Obama about the issue in an effort to attract Jewish voters, another important voting bloc in parts of Florida.

“The platform reflects the president’s position that Jerusalem is and should be the capital of Israel,” White House spokesman Jay Carney told reporters on the campaign press bus.

“It is also a case, as a matter of policy of the United States and of this administration – and of every previous administration dating back to 1967 – that the status of Jerusalem has to be decided by the (Israeli and Palestinian) parties as part of a comprehensive peace agreement.”